Oscillations in rpm

In my case, we file 1.4 16V gasoline

The same thing happened to me in my alpha, only that a mechanic told me that it was air entrance by some crack or hose, looked thoroughly until a washer that is above that it is above the injector peak was lazy, squeezed it and returned to normally lucky!

Karma, if it is a gasoline party, 1.6 16v RPM oscillations may be due to the motor meal functioning step by step that regulates an extra input of air to admission. By dirt the operation of this electric motor is slow and does not respond correctly to the commands of the central.
It is usually located near the admission butterfly, in the same piece, do you have it located at this sensor?